1. Field of the Invention
The field of the invention is pencil sharpeners and more particularly, those adapted to sharpen the rectangularly shaped carpenter's pencil.
2. Description of the Related Art
The commonly known carpenter's pencil is widely used by carpenters and has also found wide use among persons other than carpenters. For example, the pencil is becoming widely used by art students and other parties who wish to make very wide lines or wide shadings when making pencil drawings. The carpenter's pencil is characterized as being rectangular in cross-sectional shape, it being constructed of wood covering a graphite core, the core having a rectangular shape in the nature of 1/4 inch wide and 1/32 to 1/16 inch thick. For use by various parties, the graphite lead is available in various hardnesses.
While the carpenter's pencil is very desirable for use by carpenters and artists and the like, yet the problem remains as to how the pencil is to be sharpened. The most commonly used method of sharpening these pencils is to whittle away the wood and portions of the lead with a pen knife to form a rough point and then finishing up by applying a piece of sandpaper to the point. In fact, a two-stage sandpaper procedure may be used, a large grit sandpaper to firstly abraid the wood and the graphite lead and then finish with a fine sandpaper on the graphite lead and final elongated point of the pencil.
Now there have been pencil sharpeners devised for sharpening carpenter's type pencils, for example, Hamilton in U.S. Pat. No. 2,853,053 discloses such a device wherein a pair of oppositely opposed counter rotating cylindrical cutters receive the long side of the carpenter's pencil to place a point on it along the long edge of the rectangularly shaped pencil. However, no provision is made for chamfering the short sides of the rectangularly shaped carpenter's pencil to arrive at an elongated point.
In addition, Alpha, in two patents, namely U.S. Pat. Nos. 4,759,129 and 4,918,816 discloses pencil sharpeners adapted to sharpen a carpenter's pencil wherein four cutter heads are utilized to sharpen and chamfer the pencil, the four heads consisting of two pair of mutually opposed sharpening heads. By such means, all four sides of the carpenter's pencil are sharpened simultaneously. However, the devices of Alpha are indeed complicated mechanisms since all four cutter heads and their connecting gear, each mutually 90 degrees from each other, are engaged simultaneously by the prime mover resulting in a pencil sharpener costing a relatively large amount of money to construct because of the mechanical complexity of the device.
Other pencil sharpeners of the conventional type, i.e., that of placing a point upon a substantially round or octagonal shaped pencil, are shown in a number of patents, a couple of these being the 1915 Patent to Stewart, U.S. Pat. No. 1,160,091 and 1976 Patent to Aston, U.S. Pat. No. 3,965,949. Both of these pencil sharpeners utilize plantary type gears wherein a pair of pyramidal shaped rotary cutting heads each have a gear attached, the gear operating inside of a ring gear, the ring gear then turned by a hand crank.
Now Fortunati patented in 1901 a pencil sharpener, U.S. Pat. No. 673,770, alluded to above wherein the pencil is drawn across a single blade to remove wood shaving and then the lead is finally pointed with sandpaper or emery paper. The device of Fortunati catches the wood shaving and graphite particles as they are removed from the pencil. Lastly, Steinman in a 1920 patent, U.S. Pat. No. 1,333,740 illustrates a cutting machine for tailors' soap chalk wherein chalk may be machined on both sides simultaneously by two pair of oppositely opposed rotary cutters wherein the chalk is fed in at one end and taken out at the other. The chalk rests upon a carriage which carries it through the cutter machine.
It is readily apparent that devices are known which will sharpen carpenter's pencils, the devices ranging from very simple mechanism of placing a knife edge blade upon a flat surface to shave the wood of the pencil and providing sand paper for making a point to very complex mechanical devices which sharpen all four sides simultaneously.
However, it is also apparent that these devices have not been adapted by the public, perhaps because of the cost or inconvenience.
It is therefore readily apparent that there is need for apparatus which may be constructed relatively inexpensively, which is convenient to the user of the carpenter's pencil, and which is easily constructed. Such a device is provided by the instant invention.